Principles of Bioreclamation of Contaminated Ground Water and Leachates

Improper disposal of hazardous wastes has resulted in contamination of saturated and unsaturated subsurface materials (the soil/rock/ground-water system) and production of leachates. One of the least appreciated and least applied remedial treatment techniques for these contaminated materials is biological treatment. Such treatment can result in the destruction of hazardous contaminants and may be cheaper than other alternatives. Efficient bioreclamation can occur when a proper, uniform environment for the bacteria, adequate contact between the contaminated materials and the bacteria, and sufficient time to effect the degradation are provided. Maintaining the proper environment (aerobic, anaerobic, or both) includes making sure biodegradable organics are present in sufficient quantity, paying attention to microbial nutrition, keeping the pH in a suitable range, and ensuring that the bacteria can adapt to the presence of toxic substances. Selection of the bioreclamation technique to be used depends on the nature and concentration of the contaminants. The choices for above-ground treatment are suspended-growth and attached/entrapped-growth reactors. Attached/entrapped-growth systems have significant advantages for treating hazardous wastes. The three basic options for in-situ treatment are (1) enhancement of indigenous bacteria, (2) extraction-injection-recycle, and (3) creation of a biologically active barrier. Patience and an appreciation for the keys to efficient biological treatment are required to make these options work.